1. Field of the Invention
The present invention relates to a method of manufacturing a wiring substrate and a method of manufacturing an electronic component mounting structure. More specifically, the present invention relates to a method of manufacturing a wiring substrate applicable to a mount substrate for an electronic component, and to a method of manufacturing an electronic component mounting structure for mounting an electronic component on the wiring substrate.
2. Description of the Related Art
As a wiring substrate for mounting an electronic component, there has heretofore been a method of obtaining a wiring substrate by forming a desired wiring layer on a temporary substrate in a detachable manner and then separating the wiring layer from the temporary substrate. Patent Literature 1 (Japanese Unexamined Patent Publication No. 2005-236244) discloses a method of obtaining a wiring substrate, which includes the steps of: forming a copper foil on a resin substrate while attaching only a peripheral side thereof by using an adhesive layer; forming a build-up wiring layer thereon; and thereafter separating the copper foil and the build-up wiring layer from the resin substrate by cutting out an inside portion of the resin substrate, the portion being inward from the adhesive layer.
Meanwhile, Patent Literature 2 (Japanese Unexamined Patent Publication No. 2004-87701) discloses a method of obtaining a wiring substrate, which includes the steps of: attaching a detachable film and a metal base onto the carrier plate by using an adhesive layer, the detachable film being smaller than a carrier plate, and the metal base having the same size as the carrier plate; forming a metal pad on the metal base; and thereafter, separating the metal base from the detachable film and the carrier plate by cutting out a peripheral portion of the detachable film of the wiring substrate.
Moreover, Patent Literature 3 (Japanese Unexamined Patent Publication No. 2004-235323) discloses a method of obtaining a wiring substrate, which includes the steps of: laminating a first metal layer and a second metal layer on a core substrate in a way that a position of an outer periphery of the first layer is located more inward than a position of an outer periphery of the second metal layer, and attaching both layers by use of an adhesive film; forming a build-up wiring layer on the second metal layer; and thereafter, separating the second metal layer and the build-up wiring layer from the first metal layer and the core substrate by cutting out a peripheral portion of the first metal layer of the wiring substrate.
Furthermore, Patent Literature 4 (Japanese Unexamined Patent Publication No. 2005-63987) discloses a method of obtaining a wiring substrate, which includes the steps of: forming a first dielectric sheet and a second dielectric sheet, located in a way that the second dielectric sheet wraps the first dielectric sheet, on a substrate provided with a groundwork dielectric sheet on an upper side; forming a wiring layer thereon; and thereafter by cutting out an outer peripheral portion of the first dielectric sheet of the wiring substrate, and thus separating the first dielectric sheet from the substrate provided with the groundwork dielectric sheet.
However, in the above-described manufacturing methods in the prior art, in many case, wrinkles may occur in the build-up wiring layer in a series of steps of forming the build-up wiring layer on the temporary substrate in the detachable state, by virtue of heat stress applied in heating steps in the manufacturing processes, the heat stress due to differences between the thermal expansion coefficients in the structures. Accordingly, these methods are not always sufficient in reliability.